ANCHORING EFFECT OF TRIGLYCINE SULFATE CLEAVAGE PLANE ON MBBA LIQUID-CRYSTAL

On the cleavage surface of ferroelectric triglycine sulphate (TGS) nematic MBBA aligns in different ways on domains with opposite directions of spontaneous polarization. From light intensities passing through twisted nematic MBBA placed between a TGS sample and an anisotropic glass plate and director of MBBA on plus domains of TGS is determined to be close to two crystallographic directions of TGS. This alignment as well as the orientation of MBBA along 001 direction on minus domains are caused by anisotropic surface anchoring on the TGS cleavage surface. On the calculated relief, wide deep channels have been found which could account for the easy direction on minus domains. The easy direction on plus domains originates in an anisotropic interaction between nematic molecules and those of the crystal. In the paraelectric phase of TGS, both alignments described are possible.